    [Patent Document 1] JP 2002-296070 A
Retrieval of an optimum route may be made by combining several transportation means such as foot, automobile, and public transportation (for example, train, bus) and, furthermore, by considering travel states varying over time due to road traffic congestions or delays of the public transportation. To achieve such a route retrieval, there is known a technology in which a route retrieval is calculated by a center, which easily collects all the information ideally, according to the inquiry from each movable terminal (refer to Patent document 1).
However, in practically achieving such a technology, there is a problem that the load concentrates on the center with an increase in the number of movable terminals inquiring to the center. In addition, inquiring one by one requires a communication cost each time, posing a problem.